Histological changes in the alveolar structure of the rat lung after exposure to hyperoxia

ABSTRACT

The study evaluated the effect of acute and subchronic exposure to normobaric hyperphysiologic concentrations of oxygen [O2] on the alveolar structure of rat lung. This study was carried out on thirty adult male albino rats divided equally into 5 groups. Group I included unexposed rats, to be considered as control group, group II; included rats exposed to 95% O2 for 24 hours, group III rats were exposed as in group II and were left for recovery in room air for 2 weeks. Group IV included rats exposed to 60% 02 for two weeks, group rats were exposed as in group IV, then left in room air for another two weeks. The alveolar structure of the rat lung for all groups was examined by light and transmission electron microscopy. The present work demonstrated that exposure to 95% 02 for 24 hours resulted in severe pulmonary congestion with extravasation of red blood cells, edema and alteration in alveolar structure, while recovery in room air for another 2 weeks did not result in repair of the alveolar structure. On the other hand, exposure to 60% O2 for 2 weeks resulted in focal affection of the alveoli with thickened inter-alveolar septum, intense cellular infiltration together with proliferation of type II pneumocyte and deposition of interstitial collagen fibers, while recovery in room air for another 2 weeks was associated with partial improvement in alveolar structure